1. Field of the Invention
The present invention relates to a color filter substrate used for a liquid crystal display device and the like, a liquid crystal display device using the same, and a method of manufacturing a color filter substrate.
2. Description of the Related Art
A liquid crystal display device is generally provided on a personal computer, a word processor, an automobile navigation system, a small television, and the like, and demand for liquid crystal display devices has recently increased. In expansion of the market of liquid crystal display devices, contents of requirements for color filters include performances such as high definition, large size, high quality, and low cost.
A color filter substrate for such a liquid crystal display device comprises red, blue and green filters provided on a transparent substrate. In order to increase display contrast, a light shielding layer comprising chromium or the like is generally provided in the boundaries between the respective filters. At present, in order to improve the luminance of the liquid crystal display device, means for increasing the aperture of the light shielding layer for each of pixels is provided.
An example of such means is means in which the width of the light shielding layer in each of the boundaries between the adjacent filters is decreased to the limit to increase the aperture area. Although the light shielding layer is formed in a somewhat large shape due to the margin for combining the color filter substrate and an active element array substrate, in another example of means, the light shielding layer is provided on the active element array substrate side to increase the aperture for pixels.
In this way, various means for increasing the aperture of the light shielding layer are provided for increasing the luminance of the liquid crystal display device, but an increase in the aperture of the light shielding layer is accompanied with a decrease in width of the light shielding layer. Similarly, an increase in definition also causes a decrease in width of the light shielding layer.
On the other hand, as a method of manufacturing the color filter substrate, an ink-jet manufacturing method which enables a cost reduction has been proposed. Although this method comprises applying an ink to the predetermined region to form a filter of each of colors, filters of multiple colors can be obtained by the same process. However, since a plurality of color inks are simultaneously applied to the substrate, inks of different colors are mixed to possibly produce color mixing, thereby sometimes causing the problem of deteriorating yield.
A method of preventing color mixing of inks is proposed in Japanese Patent Laid-Open No. 59-75205, in which in order to prevent diffusion of ink into regions other than colored regions, a partition is formed in the boundaries between adjacent filters by photolithography. Other methods are proposed in Japanese Patent Laid-Open Nos. 4-123007 and 4-151604, in which the partition is provided with an oil-repellent and water-repellent effect. In these methods, the partition is formed by laminating a silicone rubber layer on the light shielding layer so as to prevent color mixing of different color inks on the light shielding layer. This partition prevents color mixing of inks which is caused in the coloring step of the ink jet process.
Even in the above ink-jet method of manufacturing a color filter substrate, an increase in the aperture ratio of the light shielding layer causes the need to decrease the width of the partition, thereby deteriorating the effect of preventing color mixing. The method of forming a silicone rubber layer as the partition requires many steps such as the deposition step, the exposure step and the development step for the silicone rubber layer, and the development step of removing the silicone rubber after application of inks, thereby causing an increase in cost. Therefore, the cost reducing effect of the ink jet method cannot effectively be utilized. There is also a problem in that the silicone rubber layer cannot completely be peeled.